1. Field
This disclosure is concerned generally with immune serum globulin (ISG) preparations and specifically with a highly stabilized immune serum globulin solution.
2. Prior Art
It is well known that many plasma protein preparations intended for administration to humans or animals require stabilizers to prevent denaturation or other alteration prior to use. Instability of protein preparations is particularily observed as a function of concentration. Some, like immune serum globulin preparations, are particularly unstable in relatively dilute solutions (e.g. under 15 wt % concentration) of the protein. This instability, which may be manifest by the formation of insoluble particles ("shedding"), is often increased when storage of the protein preparation is at temperatures higher than refrigerator temperature (about room temperature or higher).
Various additives for stabilizing protein preparations have been used with varying degrees of success. For example, increasing the concentration of the protein or adding another protein such as albumin has enhanced stability in some cases. Unfortunately, however, such preparations may not always be acceptable for therapeutic purposes. It is known that amino acids are useful in stabilizing some protein preparations and degraded gelatin is commonly used as a stabilizer, especially in European countries. In considering an appropriate stabilizer, consideration should be given to such factors as lack of antigenicity (possible with gelatin), effect on osmolarity of the final solution, biological activity of the specific proteins being stabilized, and the availability and cost of the stabilizer.
Various carbohydrates have been used to stabilize, facilitate processing, and/or enhance the solubility of certain biologically active protein preparations. For example, U.S. Pat. No. 2,826,533, to Fowell discloses the use of dextrose to increase the solubility of a fibrinogen preparation. U.S. Pat. No. 4,089,944 to Thomas discloses the use of a variety of carbohydrates (e.g. dextrose, mannose, galactose, fructose, lactose, sucrose, and maltose) to increase the solubility of an AHF-fibrinogen composition. The stabilization of plasma with invert sugar is disclosed in U.S. Pat. No. 3,057,781 to Mace et al.
Although dextrose has been added to immune serum globulin (e.g. Intraglobin.RTM., a modified immune serum globulin) to enhance stability and/or solubility, it has been found that, with time, the globulins in commercially available samples tend to aggregate, thereby increasing the optical density and resulting in a phenomenon commonly referred to as "shedding". As used herein, "shedding" means a visible precipitation of protein molecules. It is thought that shedding is caused by aggregation of the globulin molecules, rendering the molecules insoluble, especially in dilute solution. However, it should be noted that the exact nature of shedding is not fully understood. Shedding is undesirable since it is visually observable and indicates the possibility of inactivation or denaturation of the shedded protein and, hence, lessens the effective amount of globulin available. In addition a solution of globulin having shedded protein is unsatisfactory as a product in terms of visual appearance.
Another disadvantage associated with the use of known sugars as stabilizers in protein solutions is the fact that some sugar solutions tend to brown on heating. In addition, in some instances, it may be desirable to avoid the use of rapidly assimilated sugars such as dextrose in products intended for human use, especially for use in diabetic patients.
Quite surprisingly, we have developed a stabilized immune serum globulin preparation substantially free of shedding in dilute concentration over prolonged periods of time which utilizes a common, relatively inert sugar which, in general, can be used in amounts sufficient to assure a pharmaceutically acceptable isotonic globulin solution. This sugar can be used to stabilize immune serum globulin (ISG) preparations suitable for intramuscular administration (IMGG) or specially treated to render it suitable for intravenous administration (IVGG). Details of our stabilized preparations are disclosed herein.